1. Field of the Invention
This invention pertains generally to dentistry, and more particularly to apparatus and methods used in prosthodontics. In one manifestation, the present invention facilitates the formation of an impression of one or more impression copings or final abutments attached to dental implants.
2. Description of the Related Art
Primary or deciduous teeth form in humans very early, typically while still in the embryonic stage. As a person develops and ages, these deciduous teeth are normally lost and replaced by permanent teeth. While most teeth will typically last for decades with reasonable care, injury and disease will eventually take a toll on these permanent teeth, leading to loss thereof. This loss of permanent teeth makes chewing more difficult or in some cases impossible. In addition, the missing teeth may adversely affect a person's speech and cosmetic appearance, which in turn can adversely affect their confidence and attitude.
In some cases, a dental prosthesis may be attached directly to surrounding teeth. However, this is not always possible or practical. Where a surrounding-tooth dental prosthesis is impractical, a dental implant may be installed into a bone such as the mandibular or maxillary bones. This implant can serve as an anchor that substitutes for and thereby replaces the need for surrounding teeth. While there are a wide variety of known dental implants, such as those illustrated in at least some of the patents incorporated by reference herein below, they will typically have a mounting substructure that is anchored within the bone, and which typically terminates below, adjacent to, or slightly above the gum line. Coupled with this mounting substructure is an abutment or mounting stud. The mounting stud rises above the gum line, and provides a mounting to which a dental prosthesis may then be affixed. Prior art FIG. 8 depicts this in simplified form through one exemplary configuration and from an elevational view showing the oral cavity 1 and mandible covered with soft mucosal tissue 2 commonly referred to as the gums or gingiva. Rising from the gums 2 are three impression copings 3, 4, and 5. The actual geometry of these impression copings 3, 4, and 5 and associated implants is not critical to the present invention, and as noted may vary by manufacturer. Typical impression copings might, for exemplary purposes, have a first column or body 6 rising from the gums 2. Again, the geometry of the column 6 will vary from manufacturer to manufacturer. Columns 6 will typically each define a longitudinal axis illustrated as axes A, B, and C in FIG. 8 that each rise from or extend generally normal to the mandible or maxilla, much as a typical tooth would. Desirably, axes A, B, and C will all be parallel, but there may be some axial deviation, such as axis C in FIG. 6, which is angularly offset from axes A and B, and which deviates from normal to or perpendicular to the mandible. In addition to angular misalignment, there is also the potential for deviation in the spacing between adjacent implants.
Once the implants have been inserted into the maxilla or mandible and allowed to osseointegrate therewith, a casting is necessary to form a dental prosthesis. This casting must accurately reflect the actual locations and axial orientations of mounting studs that will be coupled to the implants, so that a dental prosthesis fabricated using the casting will properly engage and fit with the implants and mounting studs. When implants are used, there are no periodontal ligaments to absorb inaccuracies. Even very minor inaccuracies between prosthesis, mounting studs and implants can lead to bone resoprtion, loosening or breaking of prosthetic parts, or even failures in the osseointegration of the implant into bone. Consequently, it is very important to properly reproduce the patient's oral cavity 1 adjacent to the implants and any adjacent teeth. A laboratory will then be able to produce a proper dental prosthesis.
To obtain the casting, a temporary extension referred to as an impression coping is typically fastened to the implant. Next, a two-part resin-based casting composition may be applied that cures in only a few minutes. Once cured, the copings may be unscrewed or otherwise detached from the implants, and the casting removed. The casting may then be used to guide the formation of the dental prosthesis.
Undesirably, the fluid liquid resin binder used in the casting compositions is well-known to shrink both unevenly and unpredictably upon curing and hardening. In addition, the potential exists for the formation of voids in the casting which do not accurately reflect the geometry of the oral cavity 1.
To reduce unpredictable shrinkage and distortion, various fillers are known and regularly added to the resin. These fillers resist shrinkage and distortion when used at sufficiently elevated concentrations in combination with the fluid liquid resin binder. Unfortunately, they also increase the viscosity of the casting composition, changing the composition from a low viscosity fluid to a higher viscosity paste as the filler concentrations are increased. When the viscosity of the casting composition increases, it is less likely to pick up detail in the oral geometry, and more likely to retain undesirable voids. However, the high viscosity casting compositions also tend to be more durable and less likely to tear or fracture when being removed from the oral cavity. Heretofore, this has forced a dentist to choose between either low viscosity composition or high, and in the process sacrifice at least some desired features.
While FIG. 8 illustrates one exemplary configuration of impression copings, it will be understood that very different and diverse geometries may present, varying from patient to patient. Further, with more than one implant and impression coping, the need for accuracy increases. Unfortunately, the shrinkage and distortion may be additive. This means the potential exists for shrinkage adjacent one impression coping that is away from the second coping, while the shrinkage adjacent the second impression coping may also be away from the first coping. In such a case, the tolerances are effectively cut in half for a satisfactory dental prosthesis.
In view of the limitations of the prior art, several artisans have proposed different techniques for overcoming these limitations. U.S. Pat. No. 6,905,336 by Summers, entitled “Impression support system for dental implants”, the teachings and contents which are incorporated herein by reference, illustrates a semi-rigid coping reinforcement system comprising a number of crossbraces. The crossbraces must be manually inserted and adjusted to accommodate different distances required for different patients. These crossbraces must also maintain sufficient rigidity to resist the shrinkage and distortion of the impression material. As may be appreciated, the adjustability and rigidity are once again conflicting desires, and the installation time and complexity is also undesirable. A similar reinforcing structure is illustrated in U.S. Pat. No. 3,748,739 by Thibert, entitled “Oral implant stabilizer and denture support”, the teachings and contents which are incorporated herein by reference.
Another approach that has been proposed is an intra-oral scanning, such as described in U.S. Pat. No. 8,011,925 by Powell et al, entitled “Methods for manufacturing dental implant components”, the teachings and contents which are incorporated herein by reference. These systems are very expensive, difficult to operate owing to the difficulty in distinguishing saliva and other debris from tissue, and do not afford any immediate tangible product that can be inspected and validated by the dentist. Consequently, a patient may be forced to wait not only for one lab production of the prosthesis, but one or more subsequent productions until the prosthesis is perfected. It is exactly this delay that the shrinkage and distortion of prior art casting materials undesirably causes. As a result, the intra-oral scanning equipment has not been widely accepted.
In U.S. Pat. No. 6,769,913 by Hurson, entitled “Impression cap”, the teachings which are incorporated herein by reference, an impression cap is provided as a part of a kit used by a dentist. The impression cap is designed to preferably snap on to the exterior of a final abutment. The dentist then injects impression material into the cap, to fill the void between impression cap and final abutment. Next, a U-shaped impression tray filled with a second impression material is pressed over the impression cap and cured, embedding the impression cap and first material therein into the casting. While the apparatus and methods illustrated in the Hurson patent represent significant advancement over the prior art, the impression cap must be specifically designed for a particular abutment. In addition, since the impression cap surrounds the abutment and encloses it, such that the void is only accessible through a small top opening, the dentist cannot visually ascertain the fill, and instead must rely upon the impression material extruding from the impression cap as the indicator that the void has been filled. In the Hurson patent, the dentist also has little control over the thickness of the impression material from the top of the abutment to the top of the impression cap. While this thickness would preferably be consistent across the entire area filled by the impression material, to ensure flow the Hurson impression cap has a much thicker region of impression material directly above the abutment, thinning to the lower region of the abutment most adjacent to the mucosal tissue. While this variation is less than found in the prior art, such variation will tend to increase the unpredictability of shrinkage in the casting. In addition, the second impression material in the U-shaped tray will shrink and distort unpredictably, and will thereby alter the final casting geometry detrimentally.
Additional United States patents, the teachings and contents which are incorporated herein by reference, include: U.S. Pat. No. 1,478,019 by Brown, entitled “Dental impression guide”; U.S. Pat. No. 2,196,258 by Erdle, entitled “Method of molding ceramic articles”; U.S. Pat. No. 2,206,502 by Heiligman, entitled “Shaped material for casting dentures”; U.S. Pat. No. 2,579,960 by Pita et al, entitled “Method of making artificial dentures”; U.S. Pat. No. 2,755,552 by Brandau, entitled “Dental protheses, jaw-splints and jacket-crowns”; U.S. Pat. No. 3,328,879 by Bax, entitled “Means for resiliently mounting artificial teeth”; U.S. Pat. No. 3,335,495 by Wichner, entitled “Sectional preformed full dentures and method of assembling the same”; U.S. Pat. No. 3,461,560 by Hana, entitled “Method of forming a prosthetic dental appliance and an impression tray therefor”; U.S. Pat. No. 3,660,899 by Linkow, entitled “Bridge stabilizing system”; U.S. Pat. No. 3,716,918 by Tole et al, entitled “Denture coupling and method of forming coupling”; U.S. Pat. No. 3,838,187 by Thomas, entitled “Dental model construction method”; U.S. Pat. No. 3,871,804 by Cooper, entitled “Dental restoration jig”; U.S. Pat. No. 3,955,280 by Sneer, entitled “Dental implants”; U.S. Pat. No. 3,971,133 by Mushabac, entitled “Dental restoration”; U.S. Pat. No. 4,122,606 by Roman, entitled “Method and apparatus for mounting dental die models in dental stone”; U.S. Pat. No. 4,172,867 by Devault, entitled “Index pin and die spacer combination for dental model”; U.S. Pat. No. 4,204,321 by Scott, entitled “Dental post”; U.S. Pat. No. 4,242,089 by Sasaki, entitled “Dental prosthesis”; U.S. Pat. No. 4,253,835 by Ware, entitled “Post and sleeve arrangement”; U.S. Pat. No. 4,622,011 by Malek, entitled “Radicular post head comprising reversible retention and automatic positioning means”; U.S. Pat. No. 4,690,643 by Rousseau, entitled “Dental fastening device and method of use”; U.S. Pat. No. 4,744,753 by Ross, entitled “Methods for forming dental prosthesis”; U.S. Pat. No. 4,744,756 by Ross, entitled “Apparatus for forming dental prosthesis”; U.S. Pat. No. 4,892,478 by Tateosian et al, entitled “Method of preparing dental appliances”; U.S. Pat. No. 4,995,811 by Cecconi, entitled “Component part removable partial denture and method for designing and making same”; U.S. Pat. No. 5,211,561 by Graub, entitled “Coupling device for dental prothesis”; U.S. Pat. No. 5,221,204 by Kruger et al, entitled “Dental implant product and method of making”; U.S. Pat. No. 5,221,205 by Kuch, entitled “Bridge with lingual bolt locking attachment”; U.S. Pat. No. 5,234,339 by Grigereit, entitled “Implant supported prosthesis”; U.S. Pat. No. 5,234,341 by Johansen, entitled “Wearer-removable dental implant attachment”; U.S. Pat. No. 5,234,343 by Shoher et al, entitled “Moldable dental material and method”; U.S. Pat. No. 5,238,405 by Marlin, entitled “Implant collar and post system”; U.S. Pat. No. 5,242,303 by De Buck, entitled “Method for the realization of an implant prosthesis and parts hereby applied”; U.S. Pat. No. 5,259,759 by Jorneus et al, entitled “Temporary cylinder”; U.S. Pat. No. 5,439,380 by Marlin, entitled “Method of forming an abutment post”; U.S. Pat. No. 5,516,288 by Sichler et al, entitled “Device and method for attaching a member in replacement of part of a set of teeth”; U.S. Pat. No. 5,613,852 by Bavitz, entitled “Dental implant drill guide system”; U.S. Pat. No. 5,678,993 by Jeffer et al, entitled “Methods of lining dentures and denture voids and forming denture extensions”; U.S. Pat. No. 5,695,335 by Haas et al, entitled “Dental implant”; U.S. Pat. No. 5,807,100 by Thornton, entitled “Dental device having an improved deformable material and method for forming same”; U.S. Pat. No. 5,944,525 by Ura, entitled “Dental implant and method and apparatus for installing the same”; U.S. Pat. No. 5,944,526 by Liu, entitled “Method and apparatus for a dental implant system”; U.S. Pat. No. 5,947,732 by Beaty et al, entitled “Support post for use in dental implant system”; U.S. Pat. No. 6,083,005 by Taub, entitled “Method of use of natural latex emulsion”; U.S. Pat. No. 6,120,293 by Lazzara et al, entitled “Abutment for a temporary tooth”; U.S. Pat. No. 6,315,562 by Kumar, entitled “Implant carrier with gripping fingers”; U.S. Pat. No. 6,332,777 by Sutter, entitled “Device for forming a dental prosthesis”; U.S. Pat. No. 6,379,148 by Chen, entitled “Method of locating a dental implant”; U.S. Pat. No. 6,382,977 by Kumar, entitled “Snap-in impression coping”; U.S. Pat. No. 6,786,722 by Craig et al, entitled “Orthodontic modeling filler material and method”; U.S. Pat. No. 6,814,577 by Blacklock, entitled “Dental prosthesis abutment and waxing sleeve assembly”; U.S. Pat. No. 6,824,386 by Halldin et al, entitled “Components for improved impression making”; U.S. Pat. No. 6,881,360 by Stange et al, entitled “Process for producing a prosthesis and a prosthesis material”; U.S. Pat. No. 7,566,412 by Sun et al, entitled “Dental method and device”; U.S. Pat. No. 7,905,726 by Stumpel, entitled “Surgical guide for dental implant and methods therefor”; U.S. Pat. No. 8,135,492 by Yau et al, entitled “Method of making a surgical template used for a computer-guided dental implant surgery”; U.S. Pat. No. 8,454,363 by Worthington, entitled “Dental implant system”; U.S. Pat. No. 8,469,710 by Bondar, entitled “Dental implant system and method”; and U.S. Pat. No. 8,572,848 by Hayashi et al, entitled “Method for manufacturing dental implant”. In addition to the aforementioned patents, Webster's New Universal Unabridged Dictionary, Second Edition copyright 1983, is incorporated herein by reference in entirety for the definitions of words and terms used herein.